This is very useful when dealing with weapons that have the lifesteal modifier; you can run around on 100% with whatever weapons/skills you want to use, and as soon as you take a hit you can slowly regen it back up to 100% with the lifesteal weapon (conserving flask charges).
Essentially turning Mechanical Spiders into heal bots.
This can be very useful if you got 5 blueprints on one area and died, or went into a wrong area by force of habit.